Transfer image through thin len with matlab

Hello all,

i have frustrating task in my lab...

i have to generate a code in MATLAB that will get the focal length and the object distance from the lens, i.e image (1000X1000 pixels).
transfer it through the lens and, for the output it should be the result of it: inverse,magnified/shrinked version of the image. of course depends on the focal & distance of the object.
this should be done considering that the lab is on geometrical optics...

any help/reference would be appreciated